Patterning of Si substrates for Ge/Si(001) islands grown by low-energy plasma enhanced CVD

Abstract

We make use of electron beam lithography (EBL) and reactive ion etching (RIE) techniques to realize periodic masks with elements of nanometric size. Epitaxial growth of Si layers and SiGe alloys on or through such a mask leads to the formation of structures such as quantum dots and quantum rings. We will show that by making use of EBL and RIE it has been possible to obtain preferential sites for the nucleation of Ge islands on Si(001). EBL has been optimized in order to obtain circular pits with diameters ranging from 80 to 200 nm and depth from 30 to 80 nm. AFM images of the patterned substrates confirm the regularity and reproducibility of patterning in terms of form and dimension. The subsequent deposition of a thin film of Ge results in the nucleation of Ge islands at preferential sites. The precise positioning of Ge islands may be an optimal solution for obtaining self-assembled and well-ordered Ge nanostructures, leading to a number of new applications, for example within the field of quantum computing.